The present invention is related to a transmission light amount control method capable of controlling amounts of light which is received on the respective light receiving planes of a large number of photoelectric converting elements arrayed on an image pick-up element of a television camera apparatus, and also related to a television camera apparatus with employment of this transmission light amount control method.
Conventionally, as a means for varying a transmission light amount of incident light in response to a light amount of this incident light, there is such a means using filter glass. This filter glass may vary an extinction amount (a light-attenuation amount) of a transmission light amount by such a manner that while the photochromism phenomenon is utilized, a composition of a portion where light is irradiated is changed in response to a light amount of this irradiated light.
FIG. 1 shows a block structural example of a television camera apparatus using the conventional technique. In this drawing, reference numeral xe2x80x9c2xe2x80x2xe2x80x9d represents a photochromism filter glass.
Also, other than using the above-explained photochromism phenomenon, there is another camera apparatus using transmission light amount varying means capable of controlling light transmittance every arbitrary pixel, while a liquid crystal filter panel capable of varying light transmittance is arranged on a front surface of a CCD image pick-up element. For instance, such a camera apparatus is disclosed in JP-A-6-70225 and JP-A-9-51484. These two Japanese patent publications describe such an arrangement capable of controlling the light transmittance in correspondence with the pixels, while the liquid crystal panel capable of controlling the light transmittance is employed on the front surface of the image pick-up element.
In the above-described conventional technique, in such a case that the time period is relatively long, during which after the irradiation of the light is commenced, the extinction amount of the transmission light amount becomes maximum, and further, the moving picture of such a photographing object (a subject) moved in high speed is imaged, since the photochromism phenomenon is utilized, there is such a risk. That is, the transmission light amount control cannot follow the move of the high luminance level range (area) of the photographing object, and therefore, the light of this high luminance level range cannot be extincted.
As the method for adjusting the light transmittance of the liquid crystal panel employed in the camera apparatus described in JP-A-6-70225 (see embodiment modes), in the case that the incident light amount is limited by employing such a liquid crystal panel, first, the preliminary image pick-up operation is carried out, and then, the transmittance of the liquid crystal panel corresponding to such a pixel where the picture data acquired during this preliminary image pick-up operation is xe2x80x9cover-exposedxe2x80x9d data is controlled so as to be reduced. The main image pick-up operation is carried out under such a condition that this transmittance control is carried out. Then, the over-exposed data of the picture data acquired in this main image pick-up operation can be solved. However, in accordance with this control method, the following initial condition is necessarily required. That is, there is no change in the imaging light originated from the photographing object during at least the preliminary image pick-up operation and the main image pick-up operation. On the other hand, this JP-A-6-70225 does not disclose such as an arrangement capable of solving the over-exposed data problem also occurred in the case that there is a change in the imaging light originated from the photographing object due to the high-speed movement etc. of the photographing object while the preliminary image pick-up operation and the main image pick-up operation are carried out.
Also, as the method for adjusting the light transmittance of the liquid crystal panel employed in the camera apparatus described in JP-A-9-51484 (see embodiment modes), both the high luminance portion is detected, and also, such a feedback control is carried out by repeating the extinction adjustment of the light transmittance of the filter element. Then, as explained in the effects of the invention of this Japanese patent publication, since this feedback control operation is carried out, the extinction adjustment of the light transmittance of the filter element adaptable to the luminance of the high luminance portion can be correctly and easily carried out. However, this conventional adjusting method requires such an initial condition that there is no change in the imaging light originated from the photographing object while the feedback control operation is performed similar to the above adjusting method. On the other hand, this Japanese patent publication does not disclose such an arrangement capable of correctly and easily performing the extinction adjustment of the light transmittance in such a case that the imaging light originated from the photographing object is changed during the feedback control operation.
Also, this Japanese patent publication describes another adjusting method. That is, the light transmittance of the filter element may be controlled by using the inverted signal of the picture signal. However, in this adjusting method, the light transmittance is adjusted by employing such a picture signal just before 1 field period even at the highest timing. As a result, in the case that the imaging light originated from the photographing object is changed during this 1 field period, this publication never discloses such an arrangement capable of correctly and easily performing the extinction adjustment of the light transmittance similar to the above conventional method.
An object of the present invention is to provide a television camera apparatus and also a transmission light amount control method realized in such a television camera apparatus, capable of solving the above-explained problems.
Another object of the present invention is to provide such a television camera apparatus and also a transmission light amount control method employed in a television camera apparatus. That is, while such a control operation is performed so as to extinct a light amount of light of such a range which is predicted based on a temporal change of a high luminance level range, received on a light receiving plane of a photoelectric converting element, a picture signal originated from a moving photographing object portion except for this high luminance level range within the moving photographing object can be more faithfully reproduced.
To solve the above-described problems, a transmission light amount control method of the present invention is featured by that while a high luminance level range is detected from a picture signal which is acquired by imaging a moving photographing object by using an image pick-up element or acquired by imaging a subject almost in a static state that enters into a visual field of the image pick-up element by remotely rotating or elevating the image pick-up element, such a range which becomes a high luminance level is predicted based upon a temporal change and the like of this detected range, and such a transmission light amount control is carried out in such a manner that a light amount of imaging light of the predicted range, which is received by a light receiving plane of the image pick-up element, is extincted.
A television camera apparatus, according to one aspect of the present invention, is featured by such a television camera apparatus for photoelectrically converting incident light originated from a photographing object to acquire a picture signal, comprising:
an image pick-up unit containing a plurality of photoelectric converting elements;
a detection unit for detecting a range of a picture signal having a signal level higher than a predetermined level within the picture signals acquired from the image pick-up unit as a high luminance level range; and
a transmission light amount control unit for controlling incident light amounts of the imaging light from the photographing object with respect to the respective photoelectric converting elements every each of the photoelectric converting elements; wherein:
the transmission amount control unit is comprised of:
a change-component detecting unit for detecting a change component between a first high luminance level range which is detected by the detection unit at a first predetermined time instant, and a second high luminance level range which is detected by the detection unit at a second predetermined time instant after the first predetermined time instant; and
a control unit of controlling the light amount of the incident light entered into the photoelectric converting elements based upon the first predetermined time instant, the second predetermined time instant, and the detected change-component.
Also, in accordance with an example of the present invention, the transmission light amount control unit is comprised of:
a liquid crystal extinction panel for adjusting the light amounts of the light entered into the photoelectric converting elements; and
a liquid crystal drive circuit for controlling transmittance of at least a portion of the incident light with respect to the liquid crystal extinction panel.
Further, in accordance the another example of the present invention, the control unit for controlling the incident light amount with respect to the photoelectric converting elements includes a pattern generating unit; and the pattern generating unit generates a control signal used to the liquid crystal extinction panel based upon the signal derived from the change-component detecting unit.
It should be understood that the above-explained transmission light amount control operation executed in response to the predicted picture signal range may be carried out in such a way that the transmission light amount is extincted based upon at least the same range as this predicted picture signal range, or the incident light entered into the liquid crystal extinction panel 2 is not penetrated therethrough. Alternatively, the transmission light amount control operation may be carried out based upon such a range which contains the predicted picture signal range, and further, is more or less wider than this predicted picture signal range. In this alternative case, even when prediction error is produced, the correct transmission light amount control operation executed based upon this wider range may be expected, since the above-described range of the picture signal having the higher signal level than the predetermined signal level is covered by this wider range.
As described above, in accordance with the present invention, since such a transmission light amount control operation can be carried out in such a manner that the light amount of the imaging light of the range which is predicted by the temporal change of the high luminance level range, which is received by the light receiving plane of the image pick-up element, the picture signal derived from the photographing object other than this high luminance level range can be more faithfully reproduced.